The present invention relates generally to a gas pressure regulator, and more particularly to a “dome loaded” pressure regulator having an internal pilot mechanism.
One application for this invention is industrial laser applications where high gas flows are required at nearly constant pressures. One type of industrial laser application is laser cutting that typically uses a CO2 laser requiring a lasing gas that generates the laser beam and process, or assist gas, that is directed to the workpiece. Typical process gases include oxygen for cutting carbon steel and nitrogen for cutting stainless steel and alloys. Regardless of the gas used, all lasers require high process flows at an almost constant pressure to insure safe and efficient operation of the cutting apparatus. Typical laser cutting apparatus requires process gas flows as high as approximately 10,000 to 20,000 SCFH at delivery pressures up to approximately 500 PSIG.
Preferred methods for supplying process gas at high flows and constant operating pressures include using a “dome loaded” regulator in combination with an external pilot pressure regulator. A typical dome loaded regulator has a dome piston attached to a main valve that provides pressure regulation between the inlet and outlet of the regulator. Typically, a constant pressure is supplied to the top of the dome piston by a pilot regulator that receives a supply of gas from an external source connected to the inlet of the regulator. The pilot regulator supplies gas at a preselected reduced pilot pressure to an external connection on the dome regulator so that a constant downward force is applied to the dome piston. In response to the downward force from the pilot pressure acting on the dome piston, the main valve opens to allow gas to flow though the regulator at a reduced pressure. Gas flowing through the regulator applies an upward force on the bottom side of the piston to balance the constant downward force from the pilot regulator. The dome loaded regulator is configured such that pressure of the exiting gas acting on the bottom of the piston is equivalent to the pilot pressure acting on the top of the dome piston. As gas is consumed downstream of the regulator, the main valve modulates to maintain the force balance on the dome piston. For example, when gas consumption increases the outlet gas pressure starts to drop and the main valve opens allowing an increase in the volume of gas exiting the regulator. Contrastingly, when gas consumption decreases the outlet gas pressure starts to rise and the main valve closes to reduce the volume of gas exiting the regulator. The modulation of the main valve allows the regulator to maintain a constant outlet pressure throughout relatively large gas flow ranges.
Existing dome loaded regulators with external pilot regulators require external piping from the gas source to the pilot regulator and from the pilot regulator to the dome loaded regulator. The external piping required to accommodate the pilot regulator complicates the installation and increases both manufacturing and installations costs of the gas supply system. Also, the required additional pipe fittings increase the number of leak points in the gas supply system which can impact performance of the pressure regulator. Frequently, the dome loaded regulator and separate pilot regulator are mounted on a common bracket that requires additional support to accommodate the size and weight of both the dome regulator and pilot regulator.